Method and apparatus for paraffin treatment



UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR PARAFFIN TREATRIENT Pearl 0. Norman, Oklahoma City, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application March 28, 1939, Serial No. 264,652

Claims.

The invention relates to a method and apparatus for preventing the formation of paraffin in flowing wells or deep well submergible electric pump wells. It also relates to a method for indicating the presence of paraffin forming in the tubing and to a method for the removal thereof.

The object of the invention is to prevent paraffin from forming in flowing wells or electrically pumped deep Wells and provide a method that will indicate presence of any parafiin that does collect and a readily available method and apparatus for the removal of such Without pulling the tubing from the well.

There is no present method for the prevention of paraffin forming or any readily available method and apparatus for the treating or removal of parafiin in the well without removing the tubing from the well. There has never been an indicator or way of knowing that paraflin was forming in advance of the actual decrease in flowing capacity of the tubing such as disclosed by the present invention.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawing, forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same, the figure is a sectional View through the piping of the well above the surface of the ground and for a distance in the well below the surface of the ground.

At the normal temperatures existing in an oil well, parafiin is present as a liquid and flows along with the other fluids. As a well is produced, and the fluids from the well get closer to the surface of the ground, the temperature of the surroundings decrease, and in most wells, approaches the point where paraffinis normally a solid. The paraffin in solid form tends to adhere to the metal tubing and further, to build up on itself so that eventually a choke or plug is formed which greatly decreases flow or completely closes it off. When this occurs, the general practice has been to pull the tubing and clean the same with a swab or put a parafiin solvent in the tubing, dissolve the paraffin which goes to the bottom of the well again when dissolved. The present drawing shows the usual casing 9 lining the well bore which is closed at the top by the cover 5. 'Iihe cover 5 has an opening through the center to allow the tubing l2 to be placed in the well within the casing 9. The cover 5 has a recess 8 around the center thereof filled with packing material I to seal the tubing from the space between the casing 9 and tubing I2. Cover plate 6 is bolted to the cover 5 and places the packing I under pressure.

The method requires a small string of tubing as shown at I0 in the drawing, for example, a. tubing 1" in diameter extending from the well head ll inside the flow string l2, a distance of about 800 to 1,000 feet, or to the lowest point in which paraflin has been known to form. The well head H is screw threaded to the top of the flow tubing l2 and the small string of tubing l0 passes through the well head II and a packing means l3 on top of the well head closes off the annular space 14 between the tubing [0 and the flow string l2 which is generally of 2" diameter. The tubing I0 is open at the lower end so that the fluid from the well flows therethrough to the flow line on the surface of the ground not shown on the drawing. A pressure gauge [5 connects by tube I6 into the well head II and records the pressure which builds up' within the annular space M between the tubing members I0 and I2. This pressure caused by the collection of gas from the formation is proportional to or an indication of the flowing conditions in the tubing string l0. For example, if paraflin has started to collect within the small string I0, there will be increased resistance to the flow of fluid therethrough which will be reflected by an increase in pressure on the gas collected in the annular space l4 between the tubing members [0 and I2. This increase in pressure will be recorded on the gauge and will be an indication of parafiin forming in the tubing.

A gate valve l1 connects through line l8 and well head II with the annular space l4. During normal flowing operations of the well through the tubing l0, gate valve I1 is kept closed. When the pressure gauge indicates a pressure increase, or paraffin starts building up in the flow line 10 to thus obstruct flow conditions, the valve l1 may be opened and paraflin solvent is pumped through the valve l7, line l8, space [4 and up through the tubing Ill. The solvent dissolves or removes the paraffin collected in tubing 10, this being accomplished without stopping the flow of fluid from the well and further without any loss of solvent because the solvent returns to the surface of the ground along with the well flow. In this way, the paraffin solvent is not wasted in the bottom of the well as formerly, but is now concentrated on the exact area where the paralfin is collected.

Flow of paraflin solvent may be reversed and pumped down through the string of tubing l0 tit its wilt and back up the annular space [4, connection l8 and gate valve l1, if desired. This provides another mean for cleaning the string ill with high pressures and without stopping the flow from the well and without creating a serious back pressure on the well pumping equipment as the oil well flow will be up the annular space [4 along with the returning solvent.

It is also to be noted that the annular space [4 is filled with gas from the formation and gas which has come out of solution from the fluid. This gas serves to insulate the tubing string l and prevents the heat of the fluid from readily escaping to the surrounding casing. By maintaining the temperature at a higher point, the paraffin does not settle out and form on the wall of the tubing ID as readily.

It is to be noted further that the flow of liquid from the well travels through a two-inch tubing l2 until it reaches the point where the oneinch tubing I0 is set. At this point, the capacity is cut down, as the flow continues from here to the surface of the ground through the one-inch tubing [0. Since the pressure remains the same, the velocity of the fluid will increase somewhat through the tubing N. This increased Velocity of the fluid will have somewhat of a scouring effect and will not allow the paraflin to build up on the inner wall of the tubing but will tend to carry the paraffin along in the general flow of the fluid.

It is to be understood that the form of my invention, herewith shown and described, is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts ofthe apparatus may be resorted to without changing the method disclosed and without departing from the spirit of my invention, or the scope of the subjoined claims.

Having thus described my invention, I claim 1. In the method of flowing an oil well to prevent the accumulation of paraffin in flow tubing, the steps comprising placing a flow tubing from the surface of the ground to the oil reservoir, placing a second flow tubing of smaller diameter within the first mentioned flow tubing from the surface of the ground to a depth above the oil reservoir but below that at which paraffin begins to be deposited in objectionable quantities, maintaining gas in the space between the flow tubings, and producing the well from said depth through the inner flow tubing to the surface of the ground.

2. In the method of detecting the formation of a paraflin plug in oil well flow tubing, the steps comprising placing a flow tubing from the surface of the ground to the oil reservoir, placing a second flow tubing of smaller diameter within the first mentioned flow tubing from the surface of the ground to a depth above the oil reservoir but below that at which paraifin normally begins to be deposited in objectionable quantities, maintaining gas in the space between the flow tubings, producing the well from said depth through the inner flowtubing to the surface of the ground, and observing iggpgpggure ingrease on the gas in the space between the flow tubings.

3. In the method of removing paraffin deposited on the wall of oil well flow tubing without closing down production of the well, the steps comprising placing a flow tubing from the surface of the ground to the oil reservoir, placing a second flow tubing of smaller diameter within the first mentioned flow tubing from the surface of the ground to a depth above the oil reservoir but below that at which paraffin normally begins to be deposited in objectionable quantities, producing the well from said depth through the inner flow tubing to the surface of the ground, introducing a paraffin solvent into the space between the flow tubings from the surface of the ground, and returning the solvent to the surface of the ground through the inner flow tubing by the flow of fluid from the well.

4. In the method of removing paraflin deposited on the wall of oil well flow tubing without closing down production of the well, the steps comprising placing a flow tubing from the surface of the ground to the oil reservoir, placing a second flow tubing of smaller diameter within the first mentioned flow tubing from the surface of the ground to a depth above the oil reservoir but below that at which paraflin normally begins to be deposited in objectionable quantities, producing the well from said depth through the space between the flow tubings to the surface of the ground, introducinga parafiin solvent into the inner flow tubiflgfrofii'tfi'esurface of the ground, and returning the sglyent toithe surface of the ground throughth'eEpace between the flow tubings by the flow of fluid from the well.

5. In apparatus for flowing an oil well, the combination comprising a flow tubing extending from the surface of the ground to the oil producing reservoir, a second flow tubing of smaller diameter within the first mentioned flow tubing and extending from the surface of the ground to a depth above the producing reservoir but below that at which parafiin in the well fluid begins to be deposited in objectionable quantities, a pressure gauge and a source of paraflin solvent each communicating with one of the flow tubings, and a storage flow line communicating with the other flow tubing.

PEARL C. NORMAN. 

